UK Climate Rankings
A UK subsidence risk map ranking the 20 local authority areas with the highest share of postcodes on shrink-swell clay geology, based on British Geological Survey GeoClimate data. Coverage is England and Wales. Use the postcode search at the top of any page for an address-specific subsidence-risk band.
Shrink-swell subsidence is the most common form of ground movement affecting UK homes. Certain clay soils expand when wet and contract when dry. The cyclical movement can cause cracks in walls, distort door and window frames, and in severe cases require underpinning. The British Geological Survey identifies around 4.5 million UK homes as sitting in areas with some level of shrink-swell exposure. The risk is concentrated in southern and eastern England and parts of Wales, where clay-cap geology dominates.
The British Geological Survey publishes GeoClimate, a national dataset combining shrink-swell soil classification with climate projection data. Each postcode is rated across a band scale from Improbable to Probable based on the underlying geology. This ranking aggregates BGS postcode-level data to council level, ranking councils by the share of postcodes classified Probable or higher. Coverage is England and Wales. Northern Ireland data is not currently included in the LocalRisk dataset.
Much of inner and outer London sits on the London Clay Formation, a stiff blue-grey clay deposited around 50 million years ago. London Clay has a high shrink-swell potential and is the reason many London boroughs feature near the top of this ranking. The same geology extends through parts of Essex, Kent, Hertfordshire and the Thames Valley. Other clay-based geologies, including Oxford Clay, Lias Clay and Wadhurst Clay, drive subsidence exposure elsewhere in southern and central England.
UKCP18 projections indicate that UK summers are likely to become hotter and drier on average, while winters become milder and wetter. The combination of intense summer drying and intense winter rewetting amplifies the shrink-swell cycle on clay soils. The BGS GeoClimate dataset incorporates these projections into its classification, which means areas currently rated Probable are likely to remain so or shift higher rather than lower over coming decades.
A council ranking is a council-level signal. Within any council, individual postcodes can sit on different bedrock or superficial deposits, with very different shrink-swell behaviour. Old maps and trees on the property also matter (large trees draw water from clay soils, amplifying summer shrinkage). For an address-specific picture, use the BGS Property Reports service or check the LocalRisk postcode page, which combines BGS data with the postcode's other climate-risk metrics.
Shrink-swell subsidence is ground movement caused by clay soils expanding when wet and contracting when dry. The cyclical movement, often most pronounced over a single summer-winter cycle, can cause cracks in walls, distort window and door frames, and in severe cases require underpinning. It is the most common form of subsidence affecting UK homes per British Geological Survey research.
Much of London sits on the London Clay Formation, a stiff blue-grey clay with high shrink-swell potential. The same geology extends through Essex, Kent, Hertfordshire and the Thames Valley. Other clay formations across southern and central England produce similar exposure. Inner-London boroughs near deep clay deposits feature prominently in this ranking; areas built on chalk or gravel terraces (such as parts of Surrey or the South Downs) have much lower risk.
The British Geological Survey GeoClimate dataset uses a band scale from Improbable through Possible to Probable, based on the underlying soil and bedrock geology combined with climate projection data. Postcodes classified Probable contain shrink-swell soils with a measurable expectation of seasonal ground movement under projected climate. The full methodology is published by the BGS.
No. Coverage is England and Wales only. Northern Ireland data is not currently in the LocalRisk dataset. Scotland has limited shrink-swell exposure because of its underlying geology (mostly older bedrock with limited clay caps), so it would not feature prominently in this ranking even with full data.
UKCP18 climate projections indicate UK summers are likely to become hotter and drier on average, while winters become milder and wetter. The combination of intense summer drying and intense winter rewetting amplifies the shrink-swell cycle on clay soils. The BGS GeoClimate dataset incorporates these projections, which means areas currently rated Probable are likely to remain so or shift higher over coming decades rather than reducing.